升级TFS 2015.1至2017.2时需保持SQL Server 2014 Always On开启吗？

Absolutely—you can perform the TFS upgrade while your SQL Server 2014 Always On availability group remains operational, but you’ll need to follow specific steps and precautions to avoid issues. Here’s a breakdown of what you need to know:

Key Pre-Upgrade Checks & Prep #

• Confirm Compatibility: TFS 2017.2 fully supports SQL Server 2014 Always On, but make sure your SQL Server instance is patched to at least Service Pack 1 (SP1) — applying the latest cumulative update is even better to avoid known bugs.
• Full Database Backup: Take a full backup of all TFS databases in the availability group (including configuration, collection, and warehouse databases). Verify the backups are restorable before proceeding—this is your safety net if anything goes wrong.
• Adjust Always On Settings: Temporarily switch your availability group to manual failover mode for the duration of the upgrade. This prevents unexpected failovers during the database schema modifications that come with TFS upgrades, which could corrupt data or break the upgrade process.
• Verify Permissions: Ensure the account running the TFS upgrade has sysadmin privileges on the SQL Server instances hosting the availability group. The upgrade needs to modify database structures, which requires elevated permissions.

Upgrade Execution Steps #

1. Launch the TFS 2017.2 installer and select the Upgrade option.
2. When prompted to specify the database server, enter your Always On availability group listener name (not the name of an individual SQL node). The installer will automatically detect the Always On environment and target the primary replica.
3. Let the installer run through the upgrade process. It will modify the database schema on the primary replica, and these changes will automatically sync to your secondary replicas via the Always On synchronization mechanism.
4. Once the upgrade completes, verify that all databases in the availability group show a "Synchronized" status (check via SQL Server Management Studio). Confirm the TFS application layer connects successfully to the listener and all features work as expected.

Critical Notes #

• Avoid Failovers During Upgrade: Do not initiate a manual failover or allow any automatic failovers while the upgrade is in progress. Schema changes are not transaction-safe across failovers mid-process.
• Check Replica Sync: Before starting the upgrade, ensure all secondary replicas are fully synchronized with the primary. Any unsynced data could lead to inconsistencies after the upgrade.
• Rollback Plan: If the upgrade fails, restore your pre-upgrade backups to the primary replica, re-sync the secondary replicas, and troubleshoot the issue before retrying the upgrade.

内容的提问来源于stack exchange，提问作者George Altenbaugh